#include <stdio.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <pthread.h>
#include <assert.h>

/*
*线程池里所有运行和等待的任务都是一个ThreadPool
*由于所有任务都在链表里，所以是一个链表结构
*/
typedef struct task
{
    /*回调函数，任务运行时会调用此函数，注意也可声明成其它形式*/
    void *(*process)(void *arg);
    void *arg;/*回调函数的参数*/
    struct task *next;

}Task;

/*线程池结构*/
typedef struct
{
    pthread_mutex_t queue_lock;
    pthread_cond_t queue_ready;

    /*链表结构，线程池中所有等待任务*/
    Task *queue_head;

    /*是否销毁线程池*/
    int shutdown;
    pthread_t *threadid;
    /*线程池中允许的活动线程数目*/
    int max_thread_num;
    /*当前等待队列的任务数目*/
    int cur_queue_size;
}ThreadPool;


int pool_add_Task(void *(*process)(void *arg), void *arg);
void *thread_routine(void *arg);

static ThreadPool *pool = NULL;

void pool_init(int max_thread_num)
{
    pool =(ThreadPool*) malloc(sizeof(ThreadPool));

    pthread_mutex_init(&(pool->queue_lock), NULL);
    pthread_cond_init(&(pool->queue_ready), NULL);

    pool->queue_head = NULL;

    pool->max_thread_num = max_thread_num;
    pool->cur_queue_size = 0;

    pool->shutdown = 0;

    pool->threadid = (pthread_t *)malloc(max_thread_num *sizeof(pthread_t));
    int i = 0;
    for(i = 0; i < max_thread_num; i++)
    {
        pthread_create(&(pool->threadid[i]), NULL, thread_routine, NULL);
    }
}


/*向线程池中加入任务*/
int pool_add_Task(void *(*process)(void *arg), void *arg)
{
    /*构造一个新任务*/
     Task *newTask = (Task *) malloc(sizeof(Task));
     newTask->process = process;
     newTask->arg = arg;
     newTask->next = NULL;/*别忘置空*/

     pthread_mutex_lock(&(pool->queue_lock));
    /*将任务加入到等待队列中*/
     Task *member = pool->queue_head;
    if(member != NULL)
     {
        while(member->next != NULL)
             member = member->next;
         member->next = newTask;
     }
    else
     {
         pool->queue_head = newTask;
     }

     assert(pool->queue_head != NULL);

     pool->cur_queue_size++;
     pthread_mutex_unlock(&(pool->queue_lock));
    /*好了，等待队列中有任务了，唤醒一个等待线程；
     注意如果所有线程都在忙碌，这句没有任何作用*/
     pthread_cond_signal(&(pool->queue_ready));
    return 0;
}


/*销毁线程池，等待队列中的任务不会再被执行，但是正在运行的线程会一直
把任务运行完后再退出*/
int pool_destroy()
{
    if(pool->shutdown)
        return -1;/*防止两次调用*/
     pool->shutdown = 1;

    /*唤醒所有等待线程，线程池要销毁了*/
     pthread_cond_broadcast(&(pool->queue_ready));

    /*阻塞等待线程退出，否则就成僵尸了*/
    int i;
    for(i = 0; i < pool->max_thread_num; i++)
         pthread_join(pool->threadid[i], NULL);
     free(pool->threadid);

    /*销毁等待队列*/
     ThreadPool *head = NULL;
    while(pool->queue_head != NULL)
     {
         head = pool->queue_head;
         pool->queue_head = pool->queue_head->next;
         free(head);
     }
    /*条件变量和互斥量也别忘了销毁*/
     pthread_mutex_destroy(&(pool->queue_lock));
     pthread_cond_destroy(&(pool->queue_ready));

     free(pool);
    /*销毁后指针置空是个好习惯*/
     pool=NULL;
    return 0;
}


void *thread_routine(void *arg)
{
    printf("starting thread 0x%x\n", pthread_self());
    while(1)
    {
        pthread_mutex_lock(&(pool->queue_lock));
        /*如果等待队列为0并且不销毁线程池，则处于阻塞状态; 注意
        pthread_cond_wait是一个原子操作，等待前会解锁，唤醒后会加锁*/
        while(pool->cur_queue_size == 0 && !pool->shutdown)
        {
            printf("thread 0x%x is waiting\n", pthread_self());
            pthread_cond_wait(&(pool->queue_ready), &(pool->queue_lock));
        }

        /*线程池要销毁了*/
        if(pool->shutdown)
        {
            /*遇到break,continue,return等跳转语句，千万不要忘记先解锁*/
            pthread_mutex_unlock(&(pool->queue_lock));
            printf("thread 0x%x will exit\n", pthread_self());
            pthread_exit(NULL);
        }

        printf("thread 0x%x is starting to work\n", pthread_self());

        /*assert是调试的好帮手*/
        assert(pool->cur_queue_size != 0);
        assert(pool->queue_head != NULL);

        /*等待队列长度减去1，并取出链表中的头元素*/
        pool->cur_queue_size--;
        Task *Task = pool->queue_head;
        pool->queue_head = Task->next;
        pthread_mutex_unlock(&(pool->queue_lock));

        /*调用回调函数，执行任务*/
        (*(Task->process))(Task->arg);
        free(Task);
        Task = NULL;
    }
    /*这一句应该是不可达的*/
    pthread_exit(NULL);
}

//下面是测试代码
void *my_task(void *arg)
{
    printf("threadid is 0x%x, working on task %d\n", pthread_self(),*(int *) arg);
    sleep(1);/*休息一秒，延长任务的执行时间*/
    return NULL;
}

int main(int argc, char **argv)
{
    pool_init(3);/*线程池中最多三个活动线程*/

    /*连续向池中投入10个任务*/
    int *workingnum =(int *) malloc(sizeof(int) *10);
    int i;
    for(i = 0; i < 10; i++)
    {
        workingnum[i] = i;
        pool_add_Task(my_task, &workingnum[i]);
    }
    /*等待所有任务完成*/
    sleep(5);
    /*销毁线程池*/
    pool_destroy();

    free(workingnum);
    return 0;
}
